The determinist does not believe in appealing to the will, but he does believe in changing the environment. He must not say to the sinner, "Go and sin no more," because the sinner cannot help it. But he can put him in boiling oil; for boiling oil is an environment.

For a year afterward, Pronovost and his colleagues monitored what happened. The results were so dramatic that they weren't sure whether to believe them: the ten-day line-infection rate went from 11 percent to zero. So they followed patients for fifteen more months. Only two line infections occurred during the entire period. The calculated that, in this one hospital, the checklist had prevented forty-three infections and eight deaths, and saved two million dollars in costs.

The executives weren't used to venturing into patient territory, and didn't feel they belonged there. In some places, they encountered hostility, but their involvement proved crucial. In the first month, the executives discovered that chlorhexidine soap, shown to reduce line infections, was available in less than a third of the ICUs.